True, he doesn't seem a bit like Lyndon Johnson, but the way he's headed on Afghanistan, Barack Obama is threatened with a quagmire that could bog down his presidency. LBJ also had a progressive agenda in mind, beginning with his war on poverty, but it was soon overwhelmed by the cost and divisiveness engendered by a meaningless, and seemingly endless, war in Vietnam.

Meaningless is the right term for the Afghanistan war, too, because our bloody attempt to conquer this foreign land has nothing to do with its stated purpose of enhancing our national security. Just as the government of Vietnam was never a puppet of communist China or the Soviet Union, the Taliban is not a surrogate for al Qaeda. Involved in both instances was an American intrusion into a civil war whose passions and parameters we never fully have grasped and will always fail to control militarily.

The Vietnamese communists were not an extension of an inevitably hostile, unified international communist enemy, as evidenced by the fact that communist Vietnam and communist China are both our close trading partners today. Nor should the Taliban be considered simply an extension of a Mideast-based al Qaeda movement, whose operatives the United States recruited in the first place to go to Afghanistan to fight the Soviets.

Those recruits included Khalid Sheikh Mohammed, the alleged mastermind of the 9-11 attack, and financier Osama bin Laden, who met in Afghanistan as part of a force that Ronald Reagan glorified as "freedom fighters." As blowback from that bizarre, mismanaged CIA intervention, the Taliban came to power and formed a temporary alliance with the better-financed foreign Arab fighters still on the scene.

There is no serious evidence that the Taliban instigated the 9-11 attacks or even knew about them in advance. Taliban members were not agents of al Qaeda; on the contrary, the only three governments that financed and diplomatically recognized the Taliban - Saudi Arabia, the United Arab Emirates and Pakistan - all were targets of bin Laden's group.

To insist that the Taliban be vanquished militarily as a prerequisite for thwarting al Qaeda is a denial of the international fluidity of that terrorist movement. Al Qaeda, according to U.S. intelligence sources, has operated effectively in countries as disparate as Somalia, Indonesia, England and Pakistan, to name just a few. What is required to stymie such a movement is effective police and intelligence work, as opposed to deploying vast conventional military forces in the hope of finding, or creating, a conventional war to win. This last wan hope is what the effort in Afghanistan - in the last two months at its most costly point in terms of American deaths - is all about: marshaling enormous firepower to fight shadows.

The Taliban is a traditional guerrilla force that can easily elude conventional armies. Once again the generals on the ground are insisting that a desperate situation can be turned around if only more troops are committed, as Gen. Stanley A. McChrystal did in a report leaked this week. Even with U.S. forces being increased to 68,000 as part of an 110,000-strong allied army, the general states, "The situation in Afghanistan is serious." In the same sentence, however, he goes on to say that "success is achievable."

Fortunately, Defense Secretary Robert Gates is given to some somber doubts on this point, arguing that the size of the U.S. force breeds its own discontents: "I have expressed some concerns in the past about the size of the American footprint, the size of the foreign military footprint in Afghanistan," he said. "And, clearly, I want to address those issues. And we will have to look at the availability of forces, we'll have to look at costs."

I write the word fortunately because just such wisdom on the part of Robert McNamara, another defense secretary, during the buildup to Vietnam would have led him to oppose rather than abet what he ruefully admitted decades after the fact was a disastrous waste of life and treasure: 59,000 Americans dead, along with 3.4 million Indochinese, mostly innocent civilians.

I was reporting from Vietnam when that buildup began, and then as now there was an optimism not supported by the facts on the ground. Then as now there were references to elections and supporting local politicians to win the hearts and minds of people we were bombing. Then as now the local leaders on our side turned out to be hopelessly corrupt, a condition easily exploited by those we term the enemy.

Those who favor an escalation of the Afghanistan war ought to own up to its likely costs. If 110,000 troops have failed, will we need the half million committed at one point to Vietnam, which had a far less intractable terrain? And can you have that increase in forces without reinstituting the draft?

It is time for Democrats to remember that it was their party that brought America its most disastrous overseas adventure and to act forthrightly to pull their chosen president back from the abyss before it is too late.